<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta id="viewport" name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=0">
  <title>WeUI-Uploader</title>
  <link rel="stylesheet" href="https://res.wx.qq.com/open/libs/weui/0.3.0/weui.css" />
</head>
<body>
  <div class="container">
    <div class="weui_cells_title">上传</div>
    <div class="weui_cells weui_cells_form">
      <div class="weui_cell">
        <div class="weui_cell_bd weui_cell_primary">
          <div class="weui_uploader">
            <div class="weui_uploader_hd weui_cell">
              <div class="weui_cell_bd weui_cell_primary">图片上传</div>
              <div class="weui_cell_ft js_counter">0/6</div>
            </div>
            <div class="weui_uploader_bd">
              <ul class="weui_uploader_files">
                <!-- 预览图插入到这 --> </ul>
              <div class="weui_uploader_input_wrp">
                <input class="weui_uploader_input js_file" type="file" accept="image/jpg,image/jpeg,image/png,image/gif" multiple=""></div>
            </div>
          </div>
        </div>
      </div>
    </div>
  </div>
  <div class="weui_dialog_alert" style="display: none;">
    <div class="weui_mask"></div>
    <div class="weui_dialog">
      <div class="weui_dialog_hd"> <strong class="weui_dialog_title">警告</strong>
      </div>
      <div class="weui_dialog_bd">弹窗内容，告知当前页面信息等</div>
      <div class="weui_dialog_ft">
        <a href="javascript:;" class="weui_btn_dialog primary">确定</a>
      </div>
    </div>
  </div>
  <script src="https://cdn.bootcss.com/zepto/1.1.6/zepto.min.js"></script>
</body>
</html>
<script>  
  $.weui = {};  
  $.weui.alert = function(options){  
    options = $.extend({title: '警告', text: '警告内容'}, options);  
    var $alert = $('.weui_dialog_alert');  
    $alert.find('.weui_dialog_title').text(options.title);  
    $alert.find('.weui_dialog_bd').text(options.text);  
    $alert.on('touchend click', '.weui_btn_dialog', function(){  
      $alert.hide();  
    });  
    $alert.show();  
  };  
  
  $(function () {  
    // 允许上传的图片类型  
    var allowTypes = ['image/jpg', 'image/jpeg', 'image/png', 'image/gif'];  
    // 1024KB，也就是 1MB  
    var maxSize = 1024 * 1024;  
    // 图片最大宽度  
    var maxWidth = 300;  
    // 最大上传图片数量  
    var maxCount = 2;  
    $('.js_file').on('change', function (event) {  
      var files = event.target.files;  
      
        // 如果没有选中文件，直接返回  
        if (files.length === 0) {  
          return;  
        }  
        
        for (var i = 0, len = files.length; i < len; i++) {  
          var file = files[i];  
          var reader = new FileReader();  
          
            // 如果类型不在允许的类型范围内  
            if (allowTypes.indexOf(file.type) === -1) {  
              $.weui.alert({text: '该类型不允许上传'});  
              continue;  
            }  
            
            if (file.size > maxSize) {  
              $.weui.alert({text: '图片太大，不允许上传'});  
              continue;  
            }  
            
            if ($('.weui_uploader_file').length >= maxCount) {  
              $.weui.alert({text: '最多只能上传' + maxCount + '张图片'});  
              return;  
            }  
            
            reader.onload = function (e) {  
              var img = new Image();  
              img.onload = function () {  
                    // 不要超出最大宽度  
                    var w = Math.min(maxWidth, img.width);  
                    // 高度按比例计算  
                    var h = img.height * (w / img.width);  
                    var canvas = document.createElement('canvas');  
                    var ctx = canvas.getContext('2d');  
                    // 设置 canvas 的宽度和高度  
                    canvas.width = w;  
                    canvas.height = h;  
                    ctx.drawImage(img, 0, 0, w, h);  
                    var base64 = canvas.toDataURL('image/png');  
                    
                    // 插入到预览区  
                    var $preview = $('<li class="weui_uploader_file weui_uploader_status" style="background-image:url(' + base64 + ')"><div class="weui_uploader_status_content">0%</div></li>');  
                    $('.weui_uploader_files').append($preview);  
                    var num = $('.weui_uploader_file').length;  
                    $('.js_counter').text(num + '/' + maxCount);  
                    
                    // 然后假装在上传，可以post base64格式，也可以构造blob对象上传，也可以用微信JSSDK上传  
                    
                    var progress = 0;  
                    function uploading() {  
                      $preview.find('.weui_uploader_status_content').text(++progress + '%');  
                      if (progress < 100) {  
                        setTimeout(uploading, 30);  
                           console.log(ctx.drawImage);
                      }  
                      else {  
                            // 如果是失败，塞一个失败图标  
                            //$preview.find('.weui_uploader_status_content').html('<i class="weui_icon_warn"></i>');  
                            $preview.removeClass('weui_uploader_status').find('.weui_uploader_status_content').remove();  
                          }  
                        }  
                        setTimeout(uploading, 30);  
                      };  
                      
                      img.src = e.target.result;  
                    };  
                    reader.readAsDataURL(file);  
                  }  
                });  
  });  
</script>
</body>
</html>